Scientists have found new and concrete evidence that supports the theory that the extinction level event that wiped out the dinosaurs was indeed caused by a massive meteorite impact. The new evidence was uncovered by researchers from the Netherlands.
While the theory has been around for awhile, scientists have been looking for conclusive evidence to finally prove that a meteorite impact caused a sudden drop in global temperatures. This "big chill" was the main cause behind an extinction level event that wiped out almost half of all the species alive during the time of the impact. The research team was composed of scientists from a number of Dutch institutions including the Utrecht University, the Royal Netherlands Institute for Sea Research and the VU University Amsterdam. The researchers published their findings in the online journal Proceedings of the National Academy of Sciences (PNAS).
The impact event in question occurred approximately 66 million years ago. A large meteorite impacted the planet in an area now known as a part of Mexico. The impact event caused the formation of the Chicxulub crater. The crater was named after a human settlement in the area. The impact event is considered as the beginning of the Palaeogene era. Due to the huge dust clouds kicked up by the massive impact, the planet experienced a sudden drop in temperatures that lasted a few decades after the impact. This type of rapid cooling caused by an impact event is known as an "impact winter."
To uncover the newfound evidence, researchers looked at marine sediments found in the vicinity of the Chicxulub crater.
"The layer of sand and shells we found was deposited by tsunamis caused by the meteorite impact," said Utrecht University PhD student Johan Vellekoop. "In the rocks just above that layer we measured high concentrations of iridium, a mineral originating from the meteorite itself. That's how we knew for sure we were looking at the right layers."
The researchers then analyzed the lipid content found in the sediments. These lipids we extracted from the remains of single-celled organisms that were alive during the impact event. The team found that after the impact event occurred, ocean water temperatures dropped by approximately 7°C at the minimum.
"And that's only a minimum estimate; it was probably much more," Vellekoop added.. "Storms following the tsunami completely stirred the sediments up."
The new evidence uncovered by the Dutch researchers is considered as the first conclusive proof that an impact winter occurred right after the meteorite slammed into prehistoric Mexico millions of years ago.
